The material on centrist Marxism was removed from the Wikipedia article on Centrism, so I have created a new article on the former. It is very much a work in progress, so anyone reading this who is a Wikipedia editor, please work on it. It started like this:
Centrism has a specific meaning within the Marxist movement, referring to a position between a revolutionary and reformist position. For instance, the Independent Labour Party (ILP) was seen as centrist because they oscillated between advocating reaching a socialist economy through reforms and advocating revolution. The members of the so-called Two-and-a-half and Three-and-a-half Internationals, who could not choose between the reformism of the social democrat Second International and the revolutionary politics of the Communist Third International, are exemplary of centrism in this sense; instances are the Spanish Workers’ Party of Marxist Unification (POUM), ILP and Poale Zion.
Revolutionary Marxists often describe centrism in this sense as opportunistic, since it argues for a revolution at some point in the future but urges reformist practices in the mean time; Libertarian socialists and anarchists view any reformism as political opportunism because they view reformism as incapable of effecting structural changes to social organization.
The term “Centrism” also denotes positions held by some of the Bolsheviks during the 1920s. In this context, “Centrism” refers to a position between the Right Opposition (which supported the New Economic Policy and friendly relations with capitalist countries) and the Left Opposition (which supported an immediate transition to a socialist economy and world revolution). By the end of the 1920s, the two opposing factions had been defeated by Joseph Stalin who eventually gained enough support from members of the factions through the application of various ideas formed by the factions’ various leaders. (i.e. Leon Trotsky, Nikolai Bukharin, etc.)